Get express/node to loop through request sent to NOAA API

Question

So I am making a kind of API middleware for my company that will grab information from the NOAA API and then store in in my database. It does more then but that a separate part. I have set it up so that it works it will get the information and store it in my sql database perfectly The issue is the information I get is based off of zipcode. One request is the information for one zipcode. I need to be able to 'loop" through a list of zipcode one at a time and store the information in the database. I am not sure how to properly get it to work. I have tested a couple of ways but have not been able to get it to work so if someone can get me pointed in the right direction it would be appreciated.

Sorry in advance my code is not cleaned up. Everything below apiRequest.end() has little function for the question. I keep it for context.

let mysql = require('mysql');
let config = require('./config.js');
var https = require("https");
var express = require("express");
var app = express();
const port = 3000;
var fs= require('fs');
var csv = require('fast-csv');

//last test
//array will replace this zip variable 
let zip = '90012';
api(zip);

function api(zips){
//All of the parts for building the get requests url
app.get("/", function(req, response) {
  var apiKey = "gPaEVizejLlbRVbXexyWtXYkfkWkoBhd";
  let webapi = 'https://www.ncdc.noaa.gov/cdo-web/api/v2/data?';
  let datasetid="datasetid=GHCND";
  let datatypeid="&datatypeid=TMAX";
  let location="&locationid=ZIP:";
  const zipcode = zips;
  let startdate="&startdate=2019-01-01";
  let enddate="&enddate=2020-01-01";
  let units = "&units=standard";
  let limit="&limit=1000";
  let url = webapi + datasetid + datatypeid + location + zipcode + startdate + enddate + units + limit;
  var options = {
    port: 443,
    method: "GET",
    headers: {
      "token": apiKey
    }
  };

  let data = "";
//request to grab from NOAA api
  let apiRequest = https.request(url, options, function(res) {
    console.log("Connected");
    //grabing all data
    res.on("data", chunk => {
      data += chunk;
    });

    res.on("end", () => {
      console.log("data collected");
      //Format JSON data
      response.send(JSON.parse(data));
      var getData = JSON.parse(data);
      if(isEmpty(getData)){
        emptyCorrect();
      }
      dataFormat(getData);
      });
  });
  apiRequest.end();
});

//fix format for date Can add more formating if needed here
function dataFormat(formData){
  for(x in formData.results){
    let date = formData.results[x].date;
    formData.results[x].date = date.slice(0,10);
    }
  jsonToSQL(formData.results);
}

//test function is going to be used for inserting the zip
function test(){
  var content = "";
  console.log("your test worked see ***************");
  return "92507";
}


//function to add grabed JSON data into the SQL database
function jsonToSQL(datafin){
  var zipcode = zips;
  let connection = mysql.createConnection(config);

  // insert statment
  let stmt = `INSERT INTO test1(ZIPCODE,DATE, TEMP)  VALUES ?  `;
  let values = [];
  for(let x in datafin){
    values.push([zipcode,datafin[x].date,datafin[x].value]);
      }

// execute the insert statment
connection.query(stmt, [values], (err, results, fields) => {
  if (err) {
    return console.error("error");
  }
  // get inserted rows
  console.log('Row inserted:' + results.affectedRows);
});

// close the database connection
connection.end();
}


function emptyCorrect(){
  console.log("Eror correction");
  var zipcode = zips;
  let connection = mysql.createConnection(config);

  // insert statment
  let stmt = `INSERT INTO test1(ZIPCODE,DATE, TEMP)  VALUES ?  `;
  let valueE = [];
    valueE.push([zipcode,"0","No Data"]);

  // execute the insert statment
  connection.query(stmt, [valueE], (err, results, fields) => {
    if (err) {
      return console.error("error");
    }
    // get inserted rows
    console.log('Row inserted:' + results.affectedRows);
  });

  // close the database connection
  connection.end();
}

function isEmpty(obj) {
    for(var key in obj) {
        if(obj.hasOwnProperty(key))
            return false;
    }
    return true;
}

app.listen(port, () => console.log(`Example app listening on port ${port}!`))
}

Answer 1

As I understand your problem can roughly be summarized as "How to loop through asynchronous evaluations in Nodejs".

There are some options for you. I would recommend wrapping call to the NOAA API with a promise and then chain those promises. This can be done as follows:

app.get('/', async function(req, response) {
  var apiKey = 'some value';
  let webapi = 'https://www.ncdc.noaa.gov/cdo-web/api/v2/data?';
  let datasetid = 'datasetid=GHCND';
  let datatypeid = '&datatypeid=TMAX';
  let location = '&locationid=ZIP:';
  let startdate = '&startdate=2019-01-01';
  let enddate = '&enddate=2020-01-01';
  let units = '&units=standard';
  let limit = '&limit=1000';
  var options = {
    port: 443,
    method: 'GET',
    headers: {
      token: apiKey
    }
  };

  const zipCodes = ['90012', '90013']; // Place a call to your function for fetching zip codes here
  let datas = [];
  prom = Promise.resolve();
  zipCodes.forEach(zipcode => {
    prom = prom.then(() => 
      new Promise((resolve, reject) => {
        let url =
          webapi +
          datasetid +
          datatypeid +
          location +
          zipcode +
          startdate +
          enddate +
          units +
          limit;
        let apiRequest = https.request(url, options, function(res) {
          console.log('Connected');
          let data = '';
          res.on('data', chunk => {
            data += chunk;
          });

          res.on('end', () => {
            console.log('data collected for zip ' + zipcode);
            datas.push(data);
            resolve();
          });
        });
        apiRequest.end();
      })
    );
  });
  prom.then(() => {
    // All requests have now been handled sequentially
    response.send(/* You'll need to figure out what to do here */);
  });
});

An alternative is to use something like the async library for dealing with sequentially calling callbacks. The async library (https://github.com/caolan/async) describes itself as:

Async is a utility module which provides straight-forward, powerful functions for working with asynchronous JavaScript.

See e.g. Node.js: How do you handle callbacks in a loop? for a similar problem (not with regards to callign an API, but dealing with asynchronous function in a loop).